David G. Chandler and Matt Madsen. Utah State University, Dep. of Plants, Soils, and Biometeorology, 4820 Old Main Hill, Logan, UT 84322
Pinyon-juniper woodlands are an ecologically important part of arid systems in the West and an understanding of basic hydrologic processes in this ecosystem is critical for effective rangeland management. Previous studies have found shrub mounds to have higher infiltration rates than intercanopy spaces. However, few studies have investigated how hydraulic conductivity varies between or within vegetation types in this system. We hypothesized that infiltration capacity decreases with organic inputs for the sandy loam soils, such as those common to the Colorado Plateau, and would decline progressively with greater canopy cover. Measurements were performed at 30 cm increments along a 15 m line transect which intersected Juniper (Juniperus osteoperma), Ephedra (Ephedra viridis), biological soil crusts and a disturbed vehicle track. Additional measurements were made on radial transects extending out from the base of individual vegetation types including pinyon pine (Pinus edulis), big sage brush (Artemisia tridentata) and Gallet grass (Pleuraphis jamesii). Infiltration and unsaturated hydraulic conductivity were the lowest under the juniper canopy, and greatest for bare soil in the intercanopy space. However, the extent of difference in hydraulic properties varied seasonally, indicating that soil water repellency regulates the infiltration patterns in this system.
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